Gas sensing and conductivity relationship on nanoporous thin films: A CaCu3Ti4O12 case study

Abstract

In this work, CaCu 3 Ti 4 O 12 (CCTO) thin films were synthesized with the polymeric precursor method and characterized by structural (X-ray diffraction) and morphological (scanning electron microscopy) techniques. These films were composed of a single CCTO phase and presented high surface porosity. The gas sensing response and conductivity-type relationship were investigated by two different approaches. Gas sensing measurements performed at different temperatures using different atmospheres showed that the CCTO has n-type gas sensing behavior and can detect small amounts of oxidizing gases with high sensitivity and selectivity. The type of intrinsic conductivity was also investigated through thermopower measurements, which indicated intrinsic n-type conductivity in CCTO thin films prepared with the polymeric precursor method and confirmed the direct relationship between the gas sensing behavior and the intrinsic conductivity of CCTO.

Evidence of ferroelectric behaviour in CaCu3Ti4O12 thin films deposited by RF-sputtering

“…Besides the perovskite phase, no other phase was observed. Our XRD data confirm the presence of a cubic crystal system [5,[35][36][37]. The inset in Fig.…”

Ultrafast Growth of h-MoO3 Microrods and Its Acetone Sensing Performance

“…The resistance of the devices was monitored over time in a multichannel system using a data acquisition switch unit (34972A, Keysight, Santa Rosa, CA, USA) under cyclic exposure between air baseline and the premixed analyte gases in dry air at 200 • C, keeping the total gas flow rate (analyte gas plus dry synthetic air) at 100 sccm (gas flow controller GV50A, MKS, Andover, MA, USA). More details about the gas sensing setup and measurements can be found in our previous manuscripts [24,25]. Sensor signal (S) was defined as R air /R gas for reducing gas and R gas /R air for oxidizing gases, the response/recovery time was taken as the time needed to reach 90% of the final steady-state signal and the selectivity was estimated as S acetone /S interferent [26,27].…”

Influence of atmospheres on the dielectric properties of calcium copper titanate ceramics

“…CaCu 3 Ti 4 O 12 CCTO ceramics and thin films are multifunctional due to its gas and moisture sensitivity . These reports indicate that electrical impedance of CCTO aged in air at RT can change either by moisture, oxygen absorption, or due to changes in the electrode material.…”

“…2,4,[6][7][8] Surface barrier layers between sample and electrode has also been reported to have an impact in controlling the dielectric properties of CCTO. 9,10 CaCu 3 Ti 4 O 12 CCTO ceramics and thin films are multifunctional due to its gas [11][12][13] and moisture sensitivity. [14][15][16][17] These reports indicate that electrical impedance of CCTO aged in air at RT can change either by moisture, oxygen absorption, or due to changes in the electrode material.…”